Glow plug relay issue

I have a 1983 GMC 3500 6.2 Glow Plug issue.Key on, faded glow plug light, Changed relay. Old relay quit clicking. New Relay doesn't click either. The pink wire to relay is good and powers up with key on. Blue wire from relay to controller has no power. When key is turned to start (Ignition) absolutely nothing happens.

Also, when foot is off clutch voltmeter registers at 9 volts. When clutch is pressed Voltmeter goes up to 13 Volts.


Any Diesel guys out there??? I would greatly appreciate any help, please.

Not much to go on, so this is a long shot, but, check the ground strap between the engine and the chassis and body. For that matter, check all the battery connections, too.

What made you suspect the relay was/is the problem? Were the glow plugs not cycling for long enough? Not cycling at all?

Your reference to a "faded glow plug light" suggests to me that the glow plugs were cycling but perhaps for not long enough. If that's the case, was the issue constant or intermittent?

As I understand it, if the dash glow plug light is on then the glow plug harness is getting power.

I recently had a similar issue on my 83 C20 and narrowed it down to the glow plug controller or the glow plug inhibitor switch. Not wanting to jack around with it anymore I just wired up a manual bypass of the controller and operate the glow plugs with a button in the cab. There are numerous threads that will tell you exactly how to do that if you're so inclined. It was incredibly easy and cheap to do, and I couldn't be happier with the result.

Good morning. The original relay was clicking and in the start mode of the key the engine was cranking. The relay had stopped clicking. So, I figured that is had faulted. I purchased a new one, installed it. The new one does not click (cycle). The key in the start position does not engage the starter. I push in the clutch, I have full power (volts). I release clutch, I have 8-9 volts. I only have one battery hooked up. I read somewhere that I need both batteries. The blue wire has no power. I just recently purchased this truck. It has been sitting for about 3 years.


It seems as though that I might have several issues that are occurring.

Well, you do need both batteries to crank it over.

Silly question, but is your glow plug solenoid connected to the drivers side battery?

Also, the blue and pink wires go to the glow plug controller. That symptom suggests a possible controller issue.

As a first step I would install two fully charged batteries. If the solenoid still doesn't operate I would then disconnect the pink and blue wire plug from the front terminals of the solenoid. Wire one of the blade terminals to ground and touch a wire from the positive side of the battery to the other. If the solenoid clicks then you probably have a defective controller.

I don't think (emphasis on think) the clutch switch is an issue because it is allowing power to pass. The fact that the voltage is low suggests a battery issue to me; if the switch were defective it shouldn't allow any power at all.

I am by no means an expert but I hope this is of some help.

Make any headway on this?

The old round glow controllers were not very reliable. Years back MP did an article here on converting to the 85-93 relay which was far more reliable. We've got this relay in a simple kit to take care of these issues including a resistor to extend glow times in cold climates.